Mortar rounds, which normally are used with muzzle loading weapon systems, can also be used in breech loading weapon systems employing a smooth bore gun tube, but only when the angle between the axis of the gun tube and horizontal is positive and sufficiently large for the force of gravity to assure the round is in proper engagement with the breech block of the gun.
Without such engagement, the percussion primer in the mortar round will not be activated causing the gun to misfire. The problem of holding the round against the breech face is aggravated with the additional system requirement of firing mortar systems from mobile platforms at negative elevation angles, i.e., at angles below horizontal. Under those circumstances, without some means of restraint, the round would be urged by the force of gravity to move down the gun tube away from the breech.
To compensate for such problems, the prior art has employed devices, such as stub cases and clips, which are attached to normal mortar rounds. An example of a stub case is shown in U.S. Pat. No. 6,257,148, wherein the stub case is mechanically attached to the base of the mortar round. The assignee of this patent is known to also attach a stub case by elastic straps engaging both the stub case and the fins of the round.
When stub case weapon systems are fired, the stub case separates from the round. Thereafter, the stub case must be removed from the breech. Because of the relatively high temperatures generated during the firing process, there are also issues relating to disposal of the hot stub case in a safe manner.
Another ordnance manufacturer is known to utilize a clip on the fins of the mortar round which engages a mating feature machined into the gun tube to hold the round against the breech face. Such prior art arrangements introduce complications of logistics, e.g., transportation, storage, and installation, and additional cost since both current and future rounds need hardware associated with them for use in breech loading systems, while increasing the complications and cost of using such specially configured rounds in traditional muzzle loading mortar systems. In addition, such prior art arrangements do not provide a means for safe misfire ejection, for clearing the gun bore of burning embers, or for forced convection cooling of the gun tube.